Exposure apparatuses are commonly used to transfer images from a reticle onto a semiconductor wafer during semiconductor processing. A typical exposure apparatus includes an apparatus frame, a measurement system, a control system, an illumination source, an optical assembly, a reticle stage assembly, and a wafer stage assembly.
The apparatus frame typically supports the measurement system, the illumination source, the reticle stage, the optical assembly, and the wafer stage above a mounting base. The measurement system monitors the positions of the stages relative to a reference such as the optical assembly. The optical assembly projects and/or focuses the light that passes through the reticle. The reticle stage assembly precisely positions the reticle relative to the optical assembly. Somewhat similarly, the wafer stage assembly precisely positions the wafer relative to the projected image from the reticle.
The size of the images and the features within the images transferred onto the wafer from the reticle are extremely small. Accordingly, the precise positioning of the wafer and the reticle relative to the optical assembly is critical to the manufacture of high density, semiconductor wafers.
Unfortunately, mechanical vibrations and deformations in the apparatus frame of the exposure apparatus can influence the accuracy of the exposure apparatus. For example, one or more movers utilized in the stage assemblies generate reaction forces that vibrate and deform the apparatus frame of the exposure apparatus. Further, the mounting base can transfer vibration to the apparatus frame.
The vibrations and deformations in the apparatus frame can move the stages and the optical assembly out of precise relative alignment. Further, the vibrations and deformations in the apparatus frame can cause the measurement system to improperly measure the relative positions of the stages. Additionally, vibration of the optical assembly can cause deformations of the optical elements within the optical assembly and degrade the optical imaging quality. As a result thereof, the accuracy of the exposure apparatus and the quality of the integrated circuits formed on the wafer can be compromised.
One attempt to solve this problem involves the use of one or more air mounts to secure the apparatus frame to the ground. The air mounts reduce the effect of vibration of the ground causing vibration to the apparatus frame. Similarly, one or more air mounts can be used to secure the components of the exposure apparatus to the apparatus frame. Unfortunately, existing air mounts have a relatively high lateral stiffness. Moreover, existing air mounts have a relatively large foot print and require a significant amount of space.
In light of the above, there is a need for an exposure apparatus with an improved isolation system. Additionally, there is a need for a vibration isolator having relatively high lateral flexibility. Moreover, there is a need for a vibration isolator having a relatively small footprint. Further, there is a need for an exposure apparatus capable of manufacturing precision devices, such as high density, semiconductor wafers.